The present invention relates to improvements in a sealing mechanism for a rotary actuator.
In general, as shown in FIG. 12, a rotary actuator is provided with a rotor (shaft) a and a casing b having said rotor inserted therein, and is arranged to have the rotor a or the casing b pivoted about the axis thereof with respect to each other.
The rotary actuator as illustrated in FIG. 12 will now be described in more detail.
The rotor a has a pair of protrusions d, d located on the outer circumferential surface c thereof so as to be symmetrical about the axis of thereof, and also, the inner circumferential surface of the casing b is provided with a pair of protrusions which are symmetrically located about the axis of the rotor.
With such an arrangement, cylindrical chambers g1, g2, g3 and g4 are formed between the rotor a and the casing b. The cylindrical chambers g1 and g3 are internally placed under the same pressure of working fluid, while at the same time, the cylindrical chambers g2 and g4 are also put in the same fluid pressure. For example, if with the casing b fixed, the cylindrical chambers g1 and g3 are supplied with working fluid, and at the same time, the cylindrical chambers g1 and g4 have their internal working fluid discharged from them, then the rotor a is rotated in the direction of the arrow head i. Inversely, if the cylindrical chambers g2 and g4 are internally fed with fluid pressure, and at the same time, the cylindrical chambers g1 and g3 have their internal fluid pressure discharged from them, the rotor is rotated in the direction of the arrow head i.
The foregoing conventional arrangement and operation of the rotary actuator necessitated the provision of grooves k in the protrusions d, d and in the protrusions f, f to fit a sealing material m into each groove k so that a sealed condition is achieved between every two adjacent ones of the cylindrical chambers g1, g2, g3 and g4.
Each groove k is in an overall sectional configuration of a cramp iron, as shown in FIG. 13. On the other hand, a conventional sealing material is made by cutting an O-ring so as to have a bar-shaped configuration, and is inserted along and into the groove k of the foregoing sectional configuration. For this reason, as shown in FIG. 13, at corner portions n, n of the groove k, the conventional sealing material was difficult to bend at right angles and to adapt precisely to the internal shape of the groove k. This hindered the complete sealing of the groove, and caused fluid leakage.
It is therefore an object of the present invention to provide improvements in the sealing mechanism of the rotary actuator, in which fluid leakage is minimized, and the relative smooth rotation of the rotor and the casing about the axis to each other can be achieved.